JPS63217782A - Scanning converting circuit - Google Patents

Abstract

PURPOSE:To maintain the resolution of a sub-still and a sub-moving image to some degree, to prevent the increase of a scanning converting interface due to the emphasis of a contour or the like and to execute the scanning conversion of a high picture quality by controlling the time base frequency characteristic of animation filter and the vertical axis frequency characteristic of a still picture filter according to a movement detecting result. CONSTITUTION:A color TV signal of an NTSC system is inputted to the input terminal 101 of a scanning converting circuit, A/D converted to take a difference between the frames of the picture element unit of the TV signal by a movement detecting circuit 102 and a movement coefficient K to which the processings of an absolute value processing, a non-linearity conversion or the like are applied is outputted. This movement coefficient is inputted to a time base frequency characteristic setting circuit 103, a vertical axis frequency characteristic setting circuit 105 and a mixing circuit 107. The A/D converted TV signal is inputted to the animation filter 104 and the still picture filter 106, the respective filters 104, 106 are controlled by the output of the circuits 103, 105 to which the movement coefficient K is set and a signal having the respective time base and the vertical time base characteristics is inputted to the mixing circuit 107.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a scan conversion circuit for converting an interlaced television signal into a progressive scanning television signal.

BACKGROUND OF THE INVENTION In recent years, I-mprovedTV (IDTV), which receives television signals of the current NTSC system and obtains higher quality images by making full use of complaint memory, etc., has been introduced in the receiver.
) is being actively researched. One way to improve image quality is double-speed scanning conversion, which converts the 2:1 interlaced scanning of the current NTSC system into 1=1 progressive scanning for display. As a recent example, a method has been reported that performs three-mode scan conversion by adapting to the movement of video (for example, Yukihiko Achiba 9 Kazuo Ishikura ``Improved T
Study of 3-mode motion adaptation processing in V (Proceedings of the 1986 National Conference of the Television Society).

The operation of the conventional scan conversion circuit will be described below with reference to the drawings.

FIG. 6 is a block diagram of a conventional scan conversion circuit. In FIG. 6, 601 is an input terminal for interlaced television signals, 602 is a motion detection circuit, and 60
3 is a spatial axis mode filter, 604 is a time axis mode filter, 605 is an intermediate mode filter, 606 is a switch, 607 and 608 are input terminals of the switch 606, 609
is the output terminal of the switch 606, 610 is the mixing circuit, 61
1 is an output terminal of the scan conversion circuit.

Regarding the scan conversion circuit configured as described above, FIGS. 7, 8 (al, (bl, (cl) and
l, (bl.

fC), its operation will be explained below.

First, the current scanning line (having an interlaced structure) of the scanning line structure diagram of the television signal shown in FIG. 7 is input to the input terminal 601 shown in FIG. In the motion detection circuit 602, the inter-frame difference in pixel units of the input television signal is taken, and processing such as absolute value processing and non-linear transformation is performed to obtain a motion coefficient k (k=o for a complete moving image, k=1
(a completely still image) and is supplied to a switch 606 and a mixing circuit 610. Spatial axis mode filter 6
03, the input television signal is spatially interpolated by the filter shown in FIG. In the time axis mode filter 604, the input television signal is temporally interpolated by the filter shown in FIG.
08. In the intermediate mode filter 605, the input television signal is interpolated two-dimensionally in time and space by the filter shown in FIG. The DC gain of the filter is 2 because the input television signal has an interlaced structure.

In the switch 606, the input from the spatial mode filter 603 and the output from the time axis mode filter 604 are supplied to the mixing circuit 610 from the switching output terminal 609 in the MSB of the motion coefficient. In the mixing circuit 610, the output from the switch 609 and the output from the intermediate mode filter are mixed by a motion coefficient k (excluding MSB) and output to an output terminal 611.
Output from At this time, the output Xv from the spatial axis mode filter 603, the output XT from the time axis mode filter 603, and the output XVT from the intermediate mode filter 605
are mixed by motion coefficient k as shown in FIG. 9 fal.

By configuring the scan conversion circuit using three-mode filters as described above, the vertical and time-axis stop bands at motion coefficient = 0.5 (quasi-moving image or quasi-still image) are widened, and the interference caused by scan conversion becomes wider. occurrence can be avoided (see reference above).

Problems to be Solved by the Invention However, in a scan conversion circuit having a three-mode configuration as described above, the time axis 30 as shown in FIGS.
The gain of the scan conversion circuit at (Hz) is 0.5≦≦
It becomes completely O in the range of 1, and the vertical axis 525/2 (
The gain in 0≦≦0.5 is completely 0
Therefore, there is a problem in that the resolution of a quasi-still image or a quasi-moving image in the vertical axis and time axis directions deteriorates, resulting in a blurred image. Furthermore, in a conventional scan conversion circuit having a two-mode configuration (a configuration in which the intermediate mode filter 605 in FIG. 1 is omitted), FIG.
As shown in Figure 1, the motion coefficient = 0.5 and the time axis is 30.
(Hz) and vertical axis 525/2 (lines) gain is 0
．． 5, and in addition to narrowing the stop band, if high frequency emphasis (so-called contour emphasis) is further performed,
This has the problem that the disturbing components are emphasized, resulting in an extremely unsightly image.

In view of the above-mentioned problems, the present invention maintains a certain degree of resolution even in quasi-still images or quasi-moving images, and furthermore, suppresses the occurrence of interference in quasi-still images or quasi-moving images as much as possible by emphasizing high frequencies, thereby achieving high image quality. The present invention provides a scan conversion circuit that performs progressive scanning image conversion.

Means for Solving the Problems In order to solve the above problems, the scan conversion circuit of the present invention has the following steps:
a motion detection means, a still image filter, a video filter,
A vertical axis frequency characteristic setting means capable of arbitrarily setting a vertical axis high frequency characteristic of the still image filter, and a time axis frequency characteristic setting means capable of arbitrarily setting a time axis high frequency characteristic of the moving image filter. , wherein the vertical axis frequency characteristic setting value of the vertical axis frequency characteristic setting means and the time axis frequency characteristic setting value of the time axis frequency characteristic setting means are made variable in accordance with the output of the motion detecting means. It is.

Effect of the present invention With the above-described configuration, the vertical axis high frequency characteristic and the time axis high frequency characteristic are controlled by the motion coefficient k which is the output of motion detection. It is also possible to reduce the occurrence of interference due to scan conversion when high frequency characteristics are emphasized while maintaining some resolution in the vertical axis and time axis directions.

Embodiment Hereinafter, a scan conversion circuit according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a scan conversion circuit in a first embodiment of the present invention. In FIG. 1, 101 is an input terminal for interlaced television signals, 102 is a motion detection circuit, 103 is a time-axis frequency characteristic setting circuit, 104 is a moving image filter, and 105
106 is a still image filter, 107 is a mixing circuit, and 108 is an output terminal of a scan conversion circuit.

Regarding the scan conversion circuit configured as above, the following diagrams are shown in Fig. 2+a), (bl, fc), and Fig. 3 (al, (
b), (C1 and Figure 4 (al, (bl, (C
1 will be used to explain its operation.

First, the current scanning line (having an interlaced structure) of the scanning line structure diagram of the television signal shown in FIG. 7 is input to the input terminal 101 shown in FIG. In the motion detection circuit 102, the inter-frame difference in pixel units of the input television signal is taken, and processing such as absolute value processing and non-linear transformation is performed to obtain a motion coefficient k (a complete moving image when k=o, -1).
(completely still image) and is supplied to the mixing circuit 1079, the time axis frequency characteristic setting circuit 103, and the vertical axis frequency characteristic setting circuit 105. In the time axis frequency characteristic setting circuit 103, as shown in equation (1), when the motion coefficient is -0 (complete video), the time axis high frequency enhancement amount PT
0 (-1≦PTo≦1) as the time axis frequency characteristic setting value PT (-1≦PT≦1. PT=0 means flat frequency characteristic, PT=1 emphasizes high range, pT-1 cuts off high range)
is supplied to the video filter 104 as a motion coefficient of =1(
(Completely still image), time axis frequency characteristic setting value PT = -
1 (high frequency cutoff) and is supplied to the moving image filter 104.

PT=PTo-k(PTo+1> ...-[11
In the vertical axis frequency characteristic setting circuit 105, as shown in equation (2), when the motion coefficient is -1 (completely still image), the vertical axis high frequency enhancement amount (so-called vertical contour enhancement amount) P is set.
,. (-1≦Pvo≦1) as is, the vertical axis frequency characteristic setting value Pv (-1≦P, ≦1, Pv=0 is flat frequency characteristic, Pv=1 is high-frequency emphasis, Pv=-1 is high-frequency cutoff ) to the still image filter 106, and the motion coefficient =
When it is 0 (complete video), the vertical axis frequency characteristic setting value Pv-
-1 (high frequency cutoff) is supplied to the still image filter 106.

Pv=k (PVo+1)-1 (2) The video filter 104
It consists of a two-dimensional filter with 3 taps x 3 taps on the vertical axis, and as shown in Figure (b), the time axis frequency characteristic setting value P
T changes the frequency characteristics in the time axis direction. Same figure fc
1 is a frequency characteristic diagram on the vertical axis. This video filter 1
At 04, the scanning lines of the television signal are spatially interpolated, have time-domain frequency characteristics controlled by the motion coefficient k, and are supplied to the mixing circuit 107. The still image filter 106 is composed of a two-dimensional filter with 3 taps x 3 taps on the time axis and vertical axis as shown in FIG. The frequency characteristic in the vertical axis direction changes.Fcl in the figure is a frequency characteristic diagram in the time axis.In this still image filter 106, the scanning lines of the television signal are temporally interpolated and controlled by the motion coefficient k. It has a spatial axis frequency characteristic and is supplied to the mixing circuit 107.The mixing circuit 107 uses the mixing characteristic shown in FIG. The output image X5 of
Output from

As described above, according to this embodiment, the time-axis frequency characteristic setting and the vertical-axis frequency characteristic setting are determined by the motion coefficient k, which is the output of motion detection, as shown in equations (1) and (2), respectively.
Figure 4 (bl, (C1
As shown in , the time axis 30 (Hz) and the vertical axis 52 at the motion coefficient = 0.5 (semi-stationary or semi-moving image)
The gain of 5/2 (mains) can be maintained to some extent, and the gain of 5/2 (mains) can be maintained to some extent, and the high frequency characteristics are controlled by the motion coefficient even when the high frequency is emphasized (as shown by the dotted line in C1 in the same figure). In addition, high-frequency components in quasi-still images or quasi-moving images are not extremely emphasized.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is a configuration diagram of a scan conversion circuit showing a second embodiment of the present invention. In the figure, 501 is an input terminal for a color television signal, 502 is an A/D conversion circuit, 503 is a YC separation demodulation circuit, 504 is a current scan line scan conversion circuit, 505 is an interpolation scan line scan conversion circuit, and 506 is a timer. An axial compression circuit, 507 a D/A conversion circuit, and 508 a picture tube.

The operation of the scan conversion circuit configured as described above will be described below.

For example, an NTSC color television signal is input from an input terminal 501 and converted into a digital value in an A/D conversion circuit 502, and then sent to a YC separation and demodulation circuit 50.
3, the luminance signal Y is separated into the color signal C, and after the C signal is demodulated, it is supplied to the current scan line scan conversion circuit 504 and the interpolation scan line scan conversion circuit 505. Here, the current scan line scan conversion circuit 504 and the interpolation scan line scan conversion circuit 505 have the same configuration as the scan conversion circuit shown in FIG. 1, and each converts the current scan line and the interpolation scan line in parallel. Let's do it. In the current scan line scan conversion circuit 504, the current scan line A in FIG. In the interpolation scan line scan conversion circuit 505, the interpolation scan line B shown in FIG. 7 is reproduced using the scan line included in the interpolation scan line filter tap in FIG. In the time axis compression circuit 506, the reproduced current scanning line and interpolated scanning line are compressed to 172 in the time axis direction, converted into double speed forward scanning, and then supplied to the D/A conversion circuit 507. The progressive scanning television signal converted into analog values by the D/A conversion circuit 507 is sent to the picture tube 508.
It will be shown on the screen.

As described above, according to this embodiment, progressive scan conversion of an NTSC television signal can be performed.

In the first embodiment, the video filter 104 and the still image filter 106 are configured with 3 taps on the vertical axis and 3 taps on the time axis, but this can also be realized with 2 taps or 4 taps or more. be.

Furthermore, in the second embodiment, the scan conversion of the present invention can be performed only on the luminance signal Y.

Effects of the Invention As described above, the present invention improves the resolution of quasi-still images or quasi-moving images to a certain extent by controlling the time axis frequency characteristics of the video filter and the vertical axis frequency characteristics of the still image filter according to the motion detection results. Furthermore, it is possible to prevent scan conversion interference from increasing due to contour enhancement, etc., and to perform scan conversion with higher image quality.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a scan conversion circuit in the first embodiment of the present invention, FIG. 2 (al, (b), TC) is a configuration diagram and characteristic diagram of the moving image filter in FIG. 1, and FIG. al,
(b). fc) is the configuration diagram and characteristic diagram of the still image filter in Figure 1, Figure 4 (a), (bl), (C) is the mixing characteristic diagram and gain characteristic diagram at high frequencies of the mixing circuit in Figure 1. , FIG. 5 is a configuration diagram of a scan conversion circuit according to a second embodiment of the present invention, FIG. 6 is a configuration diagram of a conventional scan conversion circuit, FIG. 7 is a configuration diagram of a scanning line of a television signal, and FIG. (al, (bl
, fe) is the configuration diagram of each filter in Fig. 6, and Fig. 9 (a
l, (b), (cl is the mixed characteristic diagram of the 3-mode output in Fig. 6 and the gain characteristic diagram at high frequency. 102... Motion detection circuit, 103...
Time axis frequency characteristic setting circuit, 104... Video filter, 105... Vertical axis frequency characteristic setting circuit, 106... Still image filter, 107...
...Mixing circuit, 502...A/D conversion circuit, 5
03...yc separation and demodulation circuit, 504...
- Current scan line scan conversion circuit, 505... Interpolation scan line scan conversion circuit, 506... Time axis compression circuit, 507... D/A conversion circuit, 508...
... Picture tube, 602 ... Motion detection circuit,
603... Spatial axis mode filter, 604...
. . . Time axis mode filter, 605 . . . Intermediate mode filter, 610 . . . Mixing circuit. Name of agent: Patent attorney Toshio Nakao 1 person 1 Figure 1 Figure 2 Figure 3 Vertical axis HPF 4! Direct axis cane 2 ------m--PV= 1 (C) r
Pv・OPv・−1 0−ゎte *, c Fig. 4 (C) Fig. 6 Otsu 02 Fig. 7 n 71+I n+2 71+3 (74
-LF) Figure 8 Figure 9 (C OK 10

Claims (2)

[Claims] (1) Comprising a motion detection means, a still image filter, a moving image filter, and a vertical axis frequency characteristic setting means capable of arbitrarily setting the vertical axis high frequency characteristic of the still image filter, the output of the motion detection means A scan conversion circuit characterized in that the vertical axis frequency characteristic setting value of the vertical axis frequency characteristic setting means is made variable in accordance with the above. (2) A time-axis frequency characteristic setting means that can arbitrarily set the time-axis high frequency characteristic of the video filter, and a time-axis frequency characteristic setting value of the time-axis frequency characteristic setting means is provided according to the output of the motion detection means. 2. The scan conversion circuit according to claim 1, wherein the scan conversion circuit is made variable.